1. Field of the Invention
This invention relates to a disk device provided with an inertia latch mechanism for a head actuator.
2. Description of the Related Art
In recent years, magnetic disk devices have been widely used, for example, as high-capacity disk devices in electronic apparatuses, such as personal computers. In general, a magnetic disk device comprises a magnetic disk housed in a case, a spindle motor that supports and rotates the magnetic disk, a head actuator that supports a magnetic head, a voice coil motor (hereinafter referred as a VCM) for driving the head actuator, a substrate unit, etc. The VCM includes a voice coil attached to the head actuator and a pair of yokes and permanent magnets mounted on the case side.
Compact portable personal computers have been increasing popularity in recent years. Magnetic disk devices that are mounted in the personal computers of this type are expected to be improved in reliability against impact or the like that may be caused as they are carried about.
Proposed, therefore, is a magnetic disk device that comprises a ramp load mechanism for holding the magnetic head in a given position when the device is non-operating. The ramp load mechanism is provided with a ramp that is located outside the magnetic disk. When the magnetic disk device is non-operating, the head actuator is rotated to a retreated position on the outer periphery of the magnetic disk, whereupon a suspension runs onto the ramp. Thus, the magnetic head is held in the retreated position off the surface of the disk, so that it can be prevented from running against the disk when subjected to a shock.
Also proposed is a magnetic disk device of this type that is provided with an inertia latch mechanism, which serves to enhance the shock resistance. If the magnetic disk device suffers an impact while not operating, the inertia latch mechanism engages a head actuator to restrain it from rotating, thereby holding the actuator in a retreated position.
According to a disk drive described in Jpn. Pat. Appln. KOKAI Publication No. 2003-51165, for example, an inertia latch mechanism comprises an inertia arm and a latch arm. The inertia arm has its center of gravity off its center of rotation, so that it is rotated in both forward and reverse directions by external shock acceleration. The latch arm is urged to rotate in one direction by the rotation of the inertia arm. If the disk drive in a non-operating state is subjected to a shock, a latch claw that protrudes from the distal end of the latch arm engages a head actuator, thereby holding the actuator in a retreated position.
In the inertia latch mechanism constructed in this manner, the inertia arm and the latch arm are rockably supported by a pivot that is attached to a case. The latch arm has a latch claw that engages the head actuator. The latch claw extends substantially at right angles to the bottom surface of the case so that it can engage and disengage from the head actuator with a small movement. Further, a fulcrum portion of the inertia arm is prevented from slipping off the pivot by a pivot retaining portion that is attached to a yoke of a VCM.
A top yoke and a bottom yoke that constitute a modern VCM are optimized so that they are thinned and that gaps between permanent magnets and a coil are narrowed. By doing this, the VCM can be thinned as a whole. Since the latch claw of the inertia latch mechanism extends substantially at right angles to the case bottom surface, however, a certain dimension in the height direction must be secured. It is difficult, therefore, to combine the latch claw with the thin VCM. If the inertia latch mechanism is thinned with the reduction in thickness of the VCM, it is hard to use the vertically extending latch claw, so that the function of the latch claw cannot be maintained.